The present invention relates to a poppet valve which is directly used for supplying working fluid such as reaction gas or the like in physical and/or chemical machines or the like or which is used for pressure reduction of a vacuum chamber using such reaction gas or the like. More specifically, the present invention relates to a poppet valve with a heater which is constituted so as to prevent product from the working fluid from adhering to a valve member or the like by a heater.
In a manufacturing apparatus for semiconductors, for example, reaction gas with a high temperature is used for such a chemical processing as an etching which is transferred in a vacuum chamber, and a poppet valve is used for supplying the reaction gas or reducing pressure in the vacuum chamber. However, when the temperature of the reaction gas is lowered, the product is easy to deposit and the product adheres to the interior of a poppet valve or a valve member to lower an opening/closing accuracy of the valve. Therefore, in such a poppet valve, it is important that such a constitution is employed that deposition of product from the working fluid or adhesion thereof to the valve member and the like can be prevented.
For this reason, a various kinds of poppet valves with a heater which heats a casing, a valve member and the like by a heater to prevent adhesion of product have conventionally been proposed. In Japanese Patent No. 3005449 publication, there has been disclosed one where a band heater is wound on an outer face of a casing and a rod-shape heater is attached to a valve member for opening/closing a flow path through the interior of a hollow rod extending from the valve member. Also, in Japanese Patent No. 3012831, there has been disclosed one where a rubber heater is attached to an outer face of a casing and anther heater is attached an outer periphery of a cylindrical holding body integral with a valve member. Further, in JP-A 11-82807 publication, there has been disclosed one where a rubber heater is attached to an outer face of a casing and a flexible heater is housed in the interior of a hollow rod integral with a valve member.
In each of such conventional poppet valves, a flexible band heater or rubber heater is used as a heater for heating an outer face of the casing and this heater is wound on the outer face of the casing.
However, since these heaters are each formed by embedding a heat generating body such as a nichrome wire or the like in a thin and flexible insulating outer skin such as a silicon rubber, they are relatively expensive. In addition, since winding the heat generating body on the outer peripheral face of the casing means winding the heat generating body on the entire periphery of the casing without a gap, the length of the heat generating body becomes long, which results in excessive increase in power consumption. Also, when the heat generating body is broken, only this broken heat generating body can not be replaced with a new one and the whole heater including the outer skin must be replaced with a new one.
A technical object of the present invention is to allow the entire outer periphery of a casing of a poppet valve to be heated efficiently using an inexpensive rod-like heater.
In order to solve the above problem, a poppet valve with a heater of the present invention comprises: a valve casing which has a first main port and a second main port, a flow path connecting both the main ports and an annular valve seat provided in the flow path; a cylinder which is coupled to the valve casing; a valve member of a poppet type which is provided inside the valve casing to open/close the valve seat; a rod whose distal end portion is coupled to the valve member and whose proximal end portion extends into the interior of the cylinder; a piston which is slidably arranged in the interior of the cylinder via a sealing member and is coupled to the proximal end of the rod; a heat transfer cover which is made of heat transfer material and which covers an outer peripheral face of the valve casing so as to surround the whole valve casing; and one or more first heaters formed in a rod shape, which are built in the heat transfer cover.
According to the poppet valve of the present invention which has the above-described constitution, since the heat transfer cover is covered on the outer peripheral face of the valve casing and the rod-like first heater is built in the heat transfer cover, heat from the first heater is distributed uniformly and transferred on the whole outer peripheral face of the valve casing through the heat transfer cover. As a result, the whole outer peripheral face of the valve casing can efficiently be heated by the inexpensive rod-like heater via the heat transfer cover.
It is preferable that the heat transfer cover is formed of lightweight aluminum which is excellent in heat conductivity.
In the present invention, a heat insulating cover can be disposed on an outer face of the heat transfer cover in order to prevent heat transfer to the outside. It is preferable that the heat insulating cover has a constitution that a heat diffusing plate for diffusing heat from the heat transfer cover has been attached to an inner face of the heat insulating plate, and the heat insulating cover is attached to the heat transfer cover in a state where a constant gap has been maintained by interposing a spacer between the heat transfer cover and the heat insulating cover. It is preferable that the heat insulating plate is formed of fluoric rubber or fluoric rubber foam.
Also, in the present invention, one or more second heaters can be attached to the valve member. It is preferable that the second heaters are attached to a portion of a front face of the valve member which is positioned in an internal hole of the valve seat to face the flow path at a time of valve closing, and it is covered with a heater cover air-tightly.
Further, in the present invention, a heat transfer body provided at its distal end with a heat transfer face with which the valve member comes in contact at a valve opening position is disposed in the interior of the valve casing, and one or more third heater are attached to the heat transfer body. It is preferable that the heat transfer body is formed in a cylindrical shape and it is disposed about the rod concentrically therewith, and the third heater is accommodated in a heater hole provided in the heat transfer body.
The valve casing and the cylinder can be coupled to each other via a heat insulating portion for preventing heat transfer from the valve casing to the cylinder.